Newborns can seem to smile at the most surprising moments—while feeding, drifting off, or sleeping deeply. Are these expressions dreams, reflexes, comfort, or the first signs of connection? Newborn Smiling in Sleep explains what a sleeping infant’s facial movements can and cannot tell you, separating normal active-sleep behavior from the later social smile that emerges as babies become more alert and responsive. With clear, reassuring guidance, this book follows the changing smile from the earliest weeks through the first months. You will learn how the brain, facial muscles, feeding states, and sleep cycles shape expressions; how to observe patterns without turning them into diagnoses; and how corrected age matters for babies born prematurely. Practical checklists help you note context, breathing, color, arousal, and overall wellbeing, while careful chapters explain when a question belongs with a pediatrician or health visitor. The book also respects babies who smile less, families whose experiences differ, and parents navigating exhaustion, anxiety, grief, or uncertainty. It offers safe ways to enjoy responsive interaction without forcing expression, promising outcomes, or replacing professional care. Part of The Smile and Happiness Library.